Carbon dioxide removal device

ABSTRACT

A DEVICE FOR SELECTIVELY REMOVING C/2 DIRECTLY FROM A BREATHABLE ATOMSPHERE UNDER ZERO GRAVITY CONDITION, SAID DEVICE INCLUDING AN ANODE AND CATHODE WITH A FUSED ELECTROLYTE LAYER DISPOSED THEREBETWEEN. THE ELECTROLYTE IS ARRANGED SO AS TO BE EXPOSED, FOR A SHORT TIME, TO THE ATMOSPHERE WHEREBY THE CO2 IS ABSORBED. THEN THE ELECTROLYTE IS MOVED TO A FIELD BETWEEN THE ANODE AND CATHODE WHEREBY ABSORBED CO2 IS DECOMPOSED INTO CARBON AND OXYGEN.

May 9, 1972 J, R AYLWARD -ET AL 3,661,753

CARBON DIOXIDE REMOVAL DEVICE Filed Nov. 18, 197C United States Patent O 3,661,753 CARBON DIOXIDE REMOVAL DEVICE i John R. Aylward, Vernon, and James I. Smith, vEnfield, Conn., assignors to United Aircraft Corporation, East Hartford, Conn. Filed Nov. 18, 19,70, Ser. No. 90,533 Int. Cl. C23b 5/ 68 U.S. Cl. 204-212 ABSTRACT' oF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a device for selectively 7 Claims I scrubbing carbon dioxide directly from a gaseousrmixture and decomposing the carbon dioxide into anbonand'o'xygen, whereby the oxygen can be reused, The device has particular usefulness in a spacecraft where removal of carbon dioxide from the atmosphere is necessary and reuse of the oxygen is desirable.

Description of the prior art Previously, equipment has been devised for scrubbing carbon dioxide from the atmosphere. Such equipment was not wholly satisfactory in that it did not effectively remove significant quantities of carbon dioxide, especially under the zero gravity conditions encountered on a spacecraft. Other types of equipment required auxiliary condensors to raise the concentration of CO2y because low levels could not be removed by them.

According to the present invention, a fused electrolyte of lithium carbonate, lithium oxide and lithium chloride is heated to about ll00 F. and used to absorb carbon dioxide at low concentrations directly from a gaseous mixture. This carbon dioxide is then decomposed, in the equipment of the present invention, by electrolysis to produce solid carbon at a cathode and oxygen at an anode. The above-mentioned electrolyte is well known and described in an article by Shearer et al., Aerospace Medicine, February 1962, pp. 313-316 and U.S. Pat. 3,463,709 to Russell.

The equipment preferably utilized to effect this absorption and decomposition includes an anode, a cathode and an electrolyte. The cathode is in the shape of a circular turntable which rotates at low speeds, generally less than 100 r.p.m. It is disposed in a face-to-face relation 'with the anode which is stationary and that has an aperture formed therein for the introduction of gas and exposure of the electrolyte. The electrolyte is fused and is a thin layer held by capillary action between the cathode and the anode. The CO2 laden-gas to be scrubbed contacts the electrolyte through the aperture and rotation transports the carbon dioxide which has been absorbed at the aperture to between the anode and cathode where it is decomposed into carbon and oxygen. Oxygen diffuses through the porous anode and carbon deposits upon the cathode. With this design, a small amount of electrolyte can be used to remove fairly large quantities of carbon dioxide. The electrolyte is regenerated and the oxygen can be recycled for reuse.

3,661,753 Patented May 9, 1972 2 BRIEF vDESCRIPTION OF THE DRAWINGS PIG. l is' atop plan view of the equipment partially in cross section taken along the lines 1-1 of FIG. 2 and showing the anode -and the electrolyte which is used for scrubbing the carbon dioxide.

FIG. 2 is a cross-section view of the equipment taken along lines 2 2 of PIG. 1 showing the relative poistioning of the anode, cathode and electrolyte.

4 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, the layer of electrolyte of LigCOa-LigO-LiCl has the capacity to scrub low concentrations of CO2 directly from air via the reaction CO2-|-02 CO32. The electrolyte is supported upon a cathode 2 which can be a circular, disposable disc in the shape of a turntabley mounted upon a shaft 3 which rotates at low speeds with respect to a stationary anode 4 held by supports 14. To permit the CO2 laden air to contact the electrolyte 1, anode 4 has an aperture (shown in FIG. 1) cut from it, preferably in a pie shape section. An inlet conduit 5,'generally shaped to coincide with the shape of the aperture, provides a supply of CO2 laden air. The oxygen thatis produced'through electrolysis of the CO is vented through port 15.

Anode 4 is constructed in two layers. A conductive layer 6 is formedof a porous nickel sinter having a pore size between about 24 and 32a generally averaging about 28a.

An insulating nonconductive layer 7 is formed of porous ceramic, preferably alumina having a pore size between about 0.06 and 2.3;i, generally averaging about 0.7a. Nonconductive layer 7 is bonded to the side facing the electrolyte. The thickness of the nonconductive layer 7 is chosen so that it does not have any appreciable effect upon the potential applied across the anode and cathode. During operation of the equipment, the carbon dioxide is decomposed at the' cathode into carbon and oxide ions. The oxide ions are transported to the anode by diffusion and subsequently oxidized to oxygen gas which then passes through the pores of the anode and is discharged through port 15 in FIG. 2. Because the pore size of the conductive layer 6 of anode 4 is significantly larger than the pore size of the nonconductive layer 7 (28p. vs. 0.7p.), the oxygen bubbles which are formed on the surface of the porous nickel cannot reenter the electrolyte due to the difference in capillary forces. Since the electrolyte 1 between anode 4 and cathode 2 is also held in place by capillary forces, the device can operate in zero gravity.

Carbon is another product of the electrolysis and is deposited as a layer 8 upon the cathode 2. Since carbon is a solid, the thickness of the layer 8 increases as more carbon dioxide decomposes upon it. Electrolytic action requires a definite spacing between electrodes, however. T o achieve this spacing, shaft 3 is gradually indexed downwardly at a rate corresponding to the rate of carbon deposition. When a predetermined thickness of carbon is deposited upon the cathode 2, it can be removed from the equipment, discarded and replaced with another.

In order to keep the electrolyte in a fused condition, the assembly described above is deposed within heated oven 9. The temperature is maintained (by means not shown) at a point where optimum absorption and electrolytic decomposition takes place, generally between 950 and 1300 F. The lower portion 10 of the oven 9 is operable by means of hinge 11 so that cathode 2 can be removed.

In operation, the CO2 laden air is brought into the device after being passed through a heat exchanger and a regulator for moisture content (not shown). Since the impure air is scrubbed directly of CO2, no major auxiliary equipment, such as a carbon dioxide concentrator, is

needed. In operation, aV gas mixture containing"l-per'" cent of CO, was fed into the equipment. Current densities of 300 amps/ft.2 were imposed through power source 12 at'a voltage of 2 volts with 0.01V inch spacing between the anode and cathode. Removal of 65 percent of the CO2 was obtained and the carbon deposited as a dense layer upon the cathode. Thus it can be seen vthat the present device provides a means to remove ycarbon dioxide from an atmosphere of air.

It is apparent that modications and changes can be made by those skilled in the art. It is our intention, however, only to be limited by the scope of the appended claims. 4

What is claimed is:

1. An oxygen reclamation device capable of operating in zero gravity comprising: a cathode; means torotate said cathode upon its axis; an anode in mutuallyfacing relationship to said cathode defining a space' therebetween adapted to retain a fused electrolyte layer, the anode comprising a foraminous conductive plate'nd a forami` nous insulator bonded to the side facing said cathode;

means to impose a potential between said anode and said T--means to'maintan Ythe anode-ata predetermined disductive anode plate is porous nickel, the size of the pores in said plate being larger than the size of the pores in` to provide gas-liquidl separation said anodeinslator 5i The'de'vice according" to claim 1 wherein said aperture is formed in a substantially wedgeshapel 6. The device 'according ,to claimJ-l'further including a housing and meansto `maintain said electrolyte at a predeterminedl temperature higher than the fusion point of said electrolyte. 7. The devicefaccording to'claim 6 wherein vthe cathode is detachabl-ydisposed within said housing whereby it can be yremoved when a predetermined thickness of carbon is disposed thereon. l"

,l RferencesfCited' UNITED STATES PATENTS y2,916,425

12/1959' Fujioka'et al; 20.4-68

" 2,928,783` l 3/ 1960 Bacon 204--129- UX 3,463,709 8/1969 Russell 204-60 3,265,490

t8/ 1966 Yoshizawa et al 204-68 JOHN MACK, Primary ExaminerV j I W. I. SOLOMON,= Assistant Examiner go UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIGN Patent No. 3,661,753 Dated May 9, 1972 Inventods) John R. Aylward, James l. Smith v It is certified that error appears in the above-identified patent and that said Letters vPatent are hereby corrected as shown below:

- Add the following paragraphr tor the specification:

The invention described herein was made in the perfomance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. L+35; +2 U.S.C. 2457) Signed and sealed this 21st day offNovemberrlQYE.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOlTSCHALK- Commissioner of Patents Attesting Officer 

